


I Know That Monster

by CrystalTsuyoshi



Category: Undertale (Video Game)
Genre: Body Possession, Cults, Dancetale AU, Eventual Romance, Eventual Smut, F/M, Memory Loss, Other Additional Tags to Be Added, Reader has set look, Reader is named, Several OC's in story, Singing, Slow Burn, Slow Romance, Tentacles
Language: English
Status: In-Progress
Published: 2018-01-26
Updated: 2019-01-18
Packaged: 2019-03-09 16:48:59
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 3,698
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13485690
Author URL: https://archiveofourown.org/users/CrystalTsuyoshi/pseuds/CrystalTsuyoshi
Summary: You've never been more excited in your life than you are right now. Why? Pft, monsters are finally free and now all that hard work you've been planning for years now gets to pay off. It's gonna be an uphill battle - but you're so ready for it.What you're not ready for is feeling like your heart acting all weird around one monster. Plus you're having some really weird nightmare/memory-esque dreams. Staring said monster!None of it makes sense.So now you have to figure out how to do a balancing act you really weren't ready for! Oh and don't forget the possible threat of a doomsday cult weapon into the mix....Being a teenager isn't suppose to be this difficult...





	1. Chapter 1

**Notes for the Chapter:**

> For those reading this over here is a quick rundown: Italics is Sans. Italics and bold is Reader. Bold are the song lyrics.  
> The song in question is called "Snow Magic" by Heather Alexander [that's why it says when I look it up. But I could be wrong sorry if I am]. And some details from the song won't match up with the story perfectly and I'm sorry (notsorry) for that.

_Who in Asgore's name could be out here at this stars-awful time? The artificial sun had just peeked into the air bathing the woods in an early morning glow and someone was out there, this deep in the woods, singing? Stars help him. It was going to be a long day._

_Dancing. He saw you, a human, female if your singing voice was any indication, dancing with Gyftrot. At first, he had been worried the deer monster was rearing back for an attack. And so Sans had prepared to answer with an attack of his own to your back. But then he saw how the other monster had landed with a slight bounce in his hooves as he pranced to and fro. And you, a young woman (he shamefully had to give you the once over to know your age), were reciprocating in kind with small sways of your hips, some teetering spins, and small bunny hops, as best you could with snow up to your shins._

_During one such twirl, you spotted spotting him hiding in the tree line. And a painfully long moment of silence settled over you. Sans began a hasty retreat. No doubt his presence was distressing for you being he was a skeleton. But you just smiled at him._

_**('You can join us if you'd like,' You offer)** _

 

_-_

 

_You had always been beautiful. He'd thought that the moment he laid eyes on your face. ~~So then why was he having problems remembering...?~~_

~~_(Soft. Loving. Emerald eyes that shone with kindness and flickered with powerful determination when things got tough. A chocolate waterfall for hair. You had a voice so sweet he would get weak in the knees. And a smile that warmed him down to his SOUL.)_ ~~

 

_-_

 

_Your soul was a shining beacon of warmth to all monsters. You made them smile. They believed your words when said their freedom was close. Your voice, speaking or singing, was a melody from a heavenly place. And San loved you so much. It made his soul ache. But you'd never want him. Sans was a broken monster, he would tarnish that beautiful soul of yours._

_And Sans never wanted you or your soul to suffer like that. So he ignored the tug in his soul when he saw you. He pretended to not feel how his soul screamed at him to mark you as his. It longed to cover you in his sent and mark you with his magic so every monster knew you were his. He squashed those feelings down every time they reared their head. You were his friend. Just his friend. And everything was okay. ~~He was lying.~~_

_You sang for monsters. You danced with them. Even though you weren't really very good at it. You still did you best even if you messed up or fell over. It brought all monster-kind joy when they needed it most. You showed them not all humans were bad. And slowly, as word spread about you, the underground began to have Hope again._

  

**In the forests of the North Lands**

**Where light curtains dance at night**

**Lived a warrior named Alexi –**

**He was fair and young and bright.**

**Many maidens sighed to see him,**

**Yet Alexi dwelled alone.**

**Though they tried their best to please him**

**To their charms he was as stone.**

**Then one day within the forest**

**Young Alexi passing there**

**Met a maiden**

**like no others –**

**Tall and shining, proud and fair.**

**Hair as pale as virgin snowdrifts,**

**Eyes like ice with hidden fire.**

**From the moment that he saw her**

**He was taken with desire.**

 

_He hadn't meant for it to happen. But it just had. You'd been goofing off like normal. You shared a few bad jokes between the two of you, he'd answered in kind with a few of his own and you'd ended up admitting a giggled defeat. And then MK just blitz into you mid-step. In all of the frantic flailing and surprised yelps, he kissed you._

~~_(You tasted like the first sip of warm apple cider on a cold winter day and your magic left small crackles of delight against his teeth)_ ~~

_Words were useless but he tried nonetheless to string together a haphazard apology. His bones gave an audible rattle as he sat before you with fear and panic crossing his skull. None of this would be worth it if he lost you in his life. But he was so damn glad it happened in the end. Because it let you steal a second kiss from. And he took his third from you a moment later._

_**('I love you' you whisper.)** _

 

_-_

 

_He loved to hear you sing. And you could always be found doing so in the woods. You claimed to like it there. The peacefulness of the pines let you think of the future. The future you were busy planning for monster kind. Even he started to have hope for the days ahead. And the future you undoubtedly had together._

 

_-_

 

_You always declined his offer to stay the night at his home. He never quite understood why. It wasn't because of his brother the two of you got along so well. Hell, his cooking was even better than before because of you and some of the lessons you had been giving him when you hung out. The two of you were already like family. So then why did you prefer the company at the Inn rather than next to his side at night?_

 

_-_

 

_Another human fell one day. This time it was a child. Sans had been on a slightly romantic walk with you in the woods when they stumbled across the two of you. They were scared, they were roughed up, and they were shaking like the world would give out from under there feet at any moment. You didn't even hesitate to be at their side. The two of you spoke in whispers and you never told him what it was about. But you did sware to protect the kid with your life._

_**(A replacement for their crazy ritual. Your mind reels at the knowledge. But you don't have time. Only thing is certain: You won't let it happen, not on your fucking watch! You won't ever let them have ~~Frisk~~.)** _

 

**To Alexi's awe and gladness**

**His pale maid love in return.**

**And she would deny him nothing**

**Though her past he could not learn.**

**Nor would she once leave the forest**

**Back to his own village go.**

**Said she feared the touch of strangers,**

**Would not leave the peaceful snow.**

**Now though he would often beg her,**

**Let him much past moonrise stay.**

**But with tease and soft intrigues**

**Sent him homewards on his way.**

**Enemies had young Alexi,**

**One of them a cunning foe.**

**Noted where he spent his hours,**

**Laid an ambush in the snow.**

  

_Sans pleaded with you not to go. There was this forbidding feeling welling up in his soul and he had this suspicion it was linked to you. He argued it was a bad idea to split up, you should stay together – because if the kid looked like this what would happen to you if you got caught alone?_

_**('I'll be right back I promise. We need a healer; you're too low on magic for a shortcut.' you knew Sans would understand. But that doesn't make leaving him any easier. You're worried. A tight knot is already forming in your gut. You push past it. For all of your sakes.)** _

_In the end, he submits to your words. The dread grew in him every second you were gone. But you'd be back, you'd promised him._

 

_-_

 

_Too long._

_You had been gone way too long by this point. The kid was shivering and not even his blue hoodie was helping them. The two of them had started trudging towards Snowdin at a snail's pace. If only because the kiddo couldn't move very fast due to whatever wounds they had. You hadn't been joking, they really did need a healer. The dread Sans had felt in his soul rear its head at the sound of heavy footfalls behind him. From the same direction, the child gave the most pitiful whimper he'd ever heard and held onto his shirt even tighter._

_Six of them. They were all human adults too. Thankfully only one of them seemed armed. And wouldn't you know it? He was carting around a dusty kitchen knife in his hand. Talk about being outnumbered Sans took a wise step back to begin a retreat. He Made sure to keep himself between the kid and this group at all times. Something about that freak made his magic coil in preparation for an attack. Sans wanted to blame it on those crimson eyes. Or that large creepy grin plastered across the humans face. Damn thing was just so unsettling._

 

“ **Oh my love and life, Alexi –**

**Leave while light is in the sky!**

**There is danger in the forest –**

**Leave and do not ask me why!”**

**Young Alexi, strong Alexi –**

**Laughed away his lovers fear.**

**And he did not leave till darkness**

**Then behind him he could hear**

**Sounds of wolves that stalked his footsteps.**

**Then before him he could see**

**Men that sprang out in an ambush**

**And his mortal enemy.**

 

 _It quickly boiled down to a single fact: Sans was going to have to fight. Magic buzzed to life at the ends of his fingers in preparation to strike. But he never got the change to lift a hand because you shot past him like a bullet. Your own magic coiled around you like a thick smog of color_ ~~_(Teal)_ ~~ _with the canine unit hot on your heels. Together you came screaming down upon the six like some pack of rabid animals. The dogs howled and snarled in combat against the humans while you literally threw yourself at their leader._

_He'd never seen you so ferocious in battle before. You brought down blow, after blow, after blow, down onto the knife-wielding lunatic. Never halting for even a second. You didn't dare to give him a chance to ACT against you._

_**('No mercy! Not for you! I HATE you! So just DIE ALREADY!' your mind screams in the midst of your battle.)** _

_The canines and you drove back the attackers, but not without a price. The Dogi were slightly wounded but neither of their cuts ran too deep. A bit of dust was flaking from Lesser who yapped excitedly. They began to sing of their victory. But then you turned to face them and the canines hushed themselves as Sans' soul seized in terror._

_The blade was lodged in your chest. He watched your legs buckle from under your own weight while your coughing fit robbing you of your breath. Sans was cradling you in his arms one moment. And his blurry eye lights were blinded by tears the next. Your HP was slipping away by the second, slow enough that you had a few moments of life still but too quickly for any hope of a healer making it in time. Still Sans begged you to hang on, he told you help would be here any second, that's why you'd gone to town right? For help?_

_You explained that you hadn't been able to find Papyrus in town but the canine unit had been willing to lend you a paw. But you thanked him for being brave at a time like this. Sans couldn't understand how you could cry and smile. Didn't you understand the serious nature of the situation?! Behind him, the dogs howled, desperate to find aid for you._

_The child ~~(Frisk was the name you called out)~~ timidly approached when you called their name. One hand lifted to your chest and with a pained sound, your soul was drawn forth. He gasped at it. It was ( ~~broken)~~! But from it, you pulled forth a shinning four-pointed star. The child shook their head. You insisted. And they relented._

 

**He was one against too many,**

**But ere they could raise a sword,**

**Wolves appeared and leapt upon them**

**Like a great avenging horde!**

**Wolves lead by a raging bitch-queen**

**As white and soft as snow.**

**And Alexi much astonished**

**Watched his enemies laid low.**

“ **Oh Alexi, my Alexi –**

**Why were you so bold and proud?**

**Why did you not heed the warning**

**That I dare not speak aloud?”**

**And the wolf-bitch faced Alexi**

**As blood stained her white fur red**

**And before he drew one breath**

**His lover stood in wolfing skin.**

“ **Long I loved you with Snow magic.**

**Wrought a spell, but with one ban –**

**In my woods I'd stay a maiden**

**If I never killed a man.”**

 

 

_**('It's the only way; please understand.'**_

_**You grab their hand and put it against the SAVE point. They're just like you. You know they're gonna be alright. Dying hurts like hell. But you have to hold on, have to show them it's gonna be okay. Besides, you'll see them when they get out of the underground. Your wonky soul wasn't going to hold out much longer.** _

_**So you muster up all of your magic and determination to reach out for one last button. One you had seen in the recent days but refused to press. It's golden orange glow blinded the monsters around you as you leveled your gaze at the other human. They whimpered as their own tears finally started to show. But you held your ground. You had to be strong for them.** _

_**'Be good. Be safe. Be strong.' the edges of your sight were starting to become hazy. 'and I'll see you topside.'** _

_**They nodded and you forced their hand to push the button.** _

_**You felt the world stutter around you before it started to fade into black. As it did there was a force holding you in its vice grip. For a moment you were confused, then the pain came crashing down upon you. It felt like you were being ripped apart from the inside centralizing at your soul. The pain was so intense, so focused, you just wanted to scream out in pain or to black out and be done with it. But by the will of some cruel God, your own determination wouldn't let you.** _

**It felt like hours but it couldn't have been more than a few moments for the bright happy world you once knew was inked out by an endless void. You took your first shaking breath trying desperately to regain some control over your quaking body. Something tugged at your unresponsive limbs dragging you in a slumber so deep you feared that you might never ever wake up. If only you had the power to fight back against its encroaching intrusion on your brain. As your eyelids began to grow heavy your mind drifted back towards all of your friends in the underground.**

_**And then the darkness swallowed you up.)** _

 

“ **Now the spell I wrought is ended,”**

**And she vanished as she spoke**

**And the wolf-maid turned and fled him**

**Howling in grief as her heart broke.**

 

 

_ **~TRUE RESET~** _

 

 

**Though many maids pursue him,**

**Young Alexi dwells alone.**

**And his friends are heard to wonder**

**At how sad his face has grown.**

**Young Alexi proud no longer -  
Each day to the forest goes,**

**Seeks for something lost to hiding,**

**Raised by magic in the snows.**

 

***

 

Sans blinked the last bit of sleep out of his sockets. His mind was trying to piece together the fading dream. It similar to cupping water between his bones. Slipping away so quickly that what he could hang onto were only small droplets of information. He swiped a glove without fingers over his skull while adjusting himself. Same dream as last time, and the time before that, and so on and so forth.

Normally Sans would consider this a coincidence and nothing more. But no matter how many times he had these dreams they were the same. And in them, Frisk stood out so vividly. But not so much with the other humans. He wished he could remember more, anything really. Her face, the first letter of her name, hell he would have settle for knowing her eye color at this point. Just something besides a faceless human in his dreams.

With a defeated groan Sans placed his skull into his hands. When his phone chimed he wasn't ashamed to admit he'd been startled. And the text from his brother brought a genuine grin to his face. Seems he'd managed to sleep away most of the day without really meaning to. But with all of the excitement who could blame him? One shortcut later and he had stepped out into the surface.

It was beautiful.

Sans didn't think he would ever grow accustomed to seeing the soul-stopping colors or sights around him here on the surface. It was so big and bright and colorful and loud. He loved it. Every night he could go sit outside and gaze up at those twinkling stars. Each day meant Sans could go outside and see a bright blue sky with fluffy clouds. And every morning he got to wake up to the sounds of birds singing and machines hard at work building something new.

Although, if he could be honest for a moment, he really wouldn't mind not having to listen to all of the construction noise. It wasn't any fun hearing that at what felt like the crack of dawn each day. But then again those sounds were a reminder to him about his new found freedom.

Briefly, he let himself think back to that eventful day as he walked back home. The day Frisk had shattered the barrier and they had all stood right here to watch the setting sun. How they had intercepted a group of humans on the way down. And rather than meet with hostility they were warmly welcomed into this world.

Through them, a deal was struck and the monsters had land to call their own. Houses had started going up as quickly as the next day. It was amazing what could happen when monsters and humans worked together.

“'m home,” he called as he shut the door behind himself.

Frisk scurried out of the kitchen at the sound of his voice while Papyrus remained in the kitchen to finish up what smelled like dinner. He chuckled as the kiddo wrapped their arms around him for a tight but short hug. The stockier skeleton returned the action then slipped into the kitchen.

His younger brother was hard at work over the stove. The apron tied perfectly around his torso was complimented by the chief hat that sat slightly askew atop his skull. Sans noticed how his sibling was lightly trailing a finger over an open book with one hand. His other was gently shaking some spice into the pot he had boiling on the stove. Whatever it was smelled amazing. Looks like all of those extra cooking lessons from Toriel and Jill were paying off.

“Sans...?”

Frisk didn't often speak. They preferred ASL given they were shy around most. But when they did it was in a voice so small and so quiet it hardly ever went an octave or two above a whisper. He motioned for them to follow him back into the living room.

“yeah?”

He felt his grin tightening into more of a grimace. The way Frisk paused before continuing told him they had noticed it as well.

“Are...are you okay?”

All of the tension in his face drained away at those words. He'd been really worried for a moment. Normally when they spoke to him it was to warn him about upcoming events. Ones that were about to replay because they hadn't gone so well before. Sans was thankful for those times – but the knowledge about them having this power in their hands made him rightfully worried at times.

“oh kiddo...” a skeletal hand ruffled their brown hair. “had me really worried there for a sec,”

“Sans.” their voice was stern now. “I'm serious.”

They didn't have to tell him twice. He could see it in their eyes.

“just nightmares again, 'm fine otherwise,” he said.

His answer seemed to pacify them. Which he was thankful for because he just couldn't bring himself to tell them how much irritating this was to have these half-memory like dreams that kept haunting him. And no matter how hard he tried he just couldn't remember. For a moment they looked contemplative. Then their mouth opened and hung like that for a period of time before they spoke again.

“Do you...do you promise?”

Sans really should have been expecting that one. So he smiled back and answered with a half-truth:

“yeah, i promise,”

 

**Notes for the Chapter:**

> Right so...as of 1/18/2019 this has had a MAJOR rehaul. So comments before that date will be referring to what was written here originally.


	2. Author's Note

So...I've struggled with the story I originally had planned for this story. I couldn't get things to fit together and that was driving me nuts. And to answer this problem I had the awesome idea to just adjust things and so I did.  
The setting is still in Undertale however, now it's Dancetale AU.

I also will not be connecting this to my Underswap story...For the moment. That MIGHT change in the future but very unlikely. As it is now I'm happy with how I have this idea fleshed out, I know reader inserts have been done out the wazoo but it goes well for this idea that's been harassing my brain nonstop. My muse is at an all-time high but work still occupies most of my time, so updates will be as I can and for this, I'm very sorry. But this is here to let you know that I haven't given up, I'm still going through with this. Just had to change it up a bit.

Also, this is happening as of 1/18/2019 so any comments made in chapter 1 before that time may not make any sense to those who are just joining this story, and that reason is because; Major overhaul of the story.

Just wanted to get that out there. Thanks for being understanding and uh, sorry for making the wait time an atrocity.


End file.
